Examination for Viral Inactivation of WSSV (White Spot Syndrome Virus) Isolated in Malaysia Using Black Tiger Prawn (Penaeus monodon)

Abstract

Southeast Asia is a significant area for world shrimp culture. However, in recent years, the production of cultured shrimp has markedly decreased as a result of serious viral disease such as white spot syndrome (WSS) outbreaks. In the case of Malaysia, outbreaks of this disease have been a serious problem since 1996. As one of the preventive countermeasures against WSSV, virus inactivation has been carried out against kuruma prawn in Japan. In the recent studies, it became clear that there are differences among local strains of WSSV. Furthermore, kuruma prawn shows resistance against WSSV. For these reasons, methods to inactivate Malaysian isolates of WSSV were studied with black tiger prawn (Penaeus monodon). Viral inactivation was tested using the disinfectants formalin and ethanol, the halogenous disinfectants sodium hypochlorite and IsodineR, and also using U.V. irradiation. These chemicals were mixed with the virus and injected into healthy prawns. As a result of these experiments, no mortality was observed at the concentrations of more than 0.25 ppm formalin, 0.5% effective chloride in sodium hypochlorite, and 2.5 ppm effective povidone-iodine in IsodineR. From these results, sodium hypochlorite of halogenous disinfectants showed effective inactivation even at a low concentration (0.5 ppm). On the other hand, this virus was inactivated completely by U.V. irradiation at a dose of 3 × 104 μW·sec/cm2. These results were similar to the virus inactivation of a Japanese strain with kuruma prawn (Marsupenaeus japonicus).